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If an A320 loses an engine why does the landing category go to CAT3 single?
Following an A320 engine failure, why does the the landing category go to CAT3 single even if the APU has been started and is powering the AC bus that was lost by the failed engine?

Could someone explain the significance of "cat3 single" vs dual?

@pericynthion I'm sure that if you asked that as a new question, you'd get a good answer.

According to the forums PPRUNE, for A320, taken from here:

The power supply split function that monitors the electrical segregation of the FMGC's does not consider the APU generator as an independent electrical source. As a consequence, when an engine generator is lost the capability is downgraded to CAT 3 Single.
The electrical power supply split function monitors......
  -The two BUS TIE contactors
  -The DC TIE contactor (between DC BUS 2 and DC BAT BUS)
When one of the above contactors is closed, the FMGC considers that the power supply split is lost (independently of the APU generator)
The A330 does not have this restriction and can be CAT 3 Dual capable even with one engine generator failure as APU is considered an independent electrical source.

Also- if you dig in the FCOMof the plane, you would find that if you perform dual engine cat3 approach, and an engine fails- the buses remain split to prevent the failures from reaching the other side, and it degrades to SINGLE.
If you perform an approcah with the APU online- the electrical system is built that if a failure occurs- the bus ties close and power is managed to the whole aircraft from 1 source only- meaning the buses are not split. Hence the single.

Thanks my mistake

In case of one engine failure the buses are not split, BUS TIE applies automatically to supply the other bus with the only engine running, no matters what is the AP status. Can you provide a reference for the fact that they remain split? I can't find anything on the FCOM.


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Could abrupt flight controls input cause damage in these circumstances?
I went flying yesterday with a friend in my 1972 Grumman AA-5. She's a good copilot for someone who doesn't know much about flying. I showed her how you can pitch up and down, cause 0G, and float, which is fun. I did that when she was stretching in an awkward position to surprise her, but she took revenge and did it quite hard and abruptly while in cruise around 105 MPH without turbulence, which made us hit our heads on the canopy.
We probably didn't have our seatbelts tight enough. But could this have structurally damaged the plane? Should I tell my mechanic? It behaved  normally afterward.

Welcome to aviation.SE! I think the more important question is, did you notice anything wrong with your head? If not, then it's very unlikely there was enough force to damage the aircraft. You could discuss it with your mechanic just in case, of course.

We've all let a non-pilot passenger have a little go at the controls, but honestly if someone did this to me, pilot or not, it would be the last time they got in an aircraft with me.

I don't know @Jamiec, if the pilot is playing tricks why would the passenger not have a go? I let passengers handle the controls often, but I mandate gentle inputs, I doubt that was the case here.

Thanks a lot for your replies guys! My head was fine afterwards haha, I definitely told her (in a civilized manner) not to put abrupt inputs on the controls anymore, even though I should have made it clear before. I feel confident that the aircraft is fine, but I'll look around for any damage next time, I'll also ask my mechanic at the airport if he can have a quick look at it if I see him!

Now you know what a terrible idea it is to do "fool around" stuff with a passenger.
The AA-5's maneuvering speed is 122 MPH so you can't overstress it at 105; it will stall first (and you'd have likely snap rolled it) so you should be fine.
When in doubt, the rule of thumb is, when it's metal, if it's not permanently bent, it's good to go.  The metal structure is a big spring (elastic deformation under load and returns to its original shape below the "yield" threshold) and if you don't go past its elastic limit into the plastic range (the yield limit - permanent set to a new shape after bending) it just springs back and Bob's your uncle.  A single application of a near overload to a metal structure has no significant effect fatigue wise if you stayed in the elastic range.
If you think you might have over stressed it past the metal's yield point so there is a permanent set, there will be telltale wrinkles in the skins of the wings or tail that weren't there before. If you know what to look for, I wouldn't call for a mechanic, but if not sure what you're looking at, you should have an expert take a look.
But, like I said, a pull or push on the AA-5 at 105 mph can't overstress the airframe in the first place, so if you were really going that speed, I wouldn't worry about it.  I would just resolve to be more careful about passenger briefings and "horseplay".

I would think that stress fractures wouldn't show up as a bend, yet wouldn't be considered "good to go".

Stress fractures are from exceeding the yield limit. To get stress cracks without exceeding the yield limit, you need repeated cycles. Many many cycles. There was a CRJ900 that had an engine bird ingestion incident on takeoff in Scandinavia that made the entire back end of the airplane vibrate so bad that the the Flight Attendant strapped in at the back had arm and leg injuries from the several inches of amplitude up and down flinging her up and down like a rag doll. One of the pilots quit the business.The airplane got a structural inspection; nothing was bent (or cracked) so back in service.

I agree that you won't bend the metal spar on the AA-5 --  it's a single cylinder that runs through the fuselage and wing.  The only issue might be the wing skins which are bonded composite.  Wing flex puts shear loads along the bonding areas which can cause delamination of the skin, especially along the trailing edge.  It's a common issue and is something that should be checked in every annual inspection according to the IA that did the inspections on the AA-5 that belonged to a club where I was a member.

I think you mean bonded aluminum.  Yeah the bonds have very low peel strength as well which required rivets to be added to skin corners under an AD I believe.  The Tiger was an amazing airplane in its day, but personally, I wouldn't touch an aluminum bonded aircraft, although transport airplanes use bonded skin laminations in fuselages sometimes.  Riveted airplane pretty much last forever if you don't park them outside.

What is the Va (Maneuvering Speed) of your aircraft at that weight? I would not think that an abrupt deflection of one set of control surfaces would cause structural damage at less than 100 knots. Especially if it were not a full deflection. A trainer type aircraft like that should be able to withstand up to 1.52 negative Gs. Maybe an A&P on here can give more insight. But, when in doubt, whip it out (that credit card for your A&P bill).
Here is a fun and very useful/informative little exercise. Get to a cruise altitude of at least 3000 feet AGL or higher. Advance the throttle to full and establish yourself in Vy (or even better, a Vx) climb. Once you are fully established in the climb, retard the throttle back to idle and count to 3 seconds before doing or changing anything. You will be surprised how hard you will have to nose the aircraft over to prevent a stall and establish Vg. You may even experience negative Gs similar to the ones you experienced earlier. If you don’t have spin training, only do this with a current and proficient CFI.

Sounds like a strong lack of angle-of-attack stability?  Would, say, a Cessna 172 flown with two people in the front seat give this result?

@quietflyer - I am not quite sure what your question is. Could you restate it? If you are asking if you could experience negative G-loading in a Cessna 172, the answer is yes. The exercise I described simulates an engine loss on takeoff including a startle response. Unlike a power-on or a power-off stall, you do not have the option of using thrust from engine power to recover. Airspeed bleeds off quickly. And, your only option is to pitch down aggressively to avoid a stall.

@quietflyer Less likely.Grumman singles characteristically have lighter control forces in all axes than similar Cessnas and Pipers.  It was part of their appeal when they came out, besides speed for the power.There is a still a strong positive stick force gradient when pulling G, but it's a bit shallower than something like a 172, and a 20lb yank on the column could be expected to make a harder vertical acceleration in the Grumman than the Cessna.  Also a new pilot might interpret something less than 2Gs applied suddenly as 3 or 4. Less than a G negative will result in a sharp rap on the head.

+1 for "when in doubt, contact your A&P" not some (very knowledgeable) internet strangers.

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Could a triplane fly using a dihedral wing in the middle?

I wonder if a triplane glider whose front view is shown in the figure can be built and flown successfully.  As you can see, the middle wing has a dihedral angle, but the top and bottom wings do not.  The vertical lines represent structural members.  The idea behind this strange design is that a box-shape with diagonal members is structurally very strong, hence my interest.  I realize that the structural members at each end will contribute to the drag, even if they have a streamlined shape.  I also realize that every corner of this shape will not produce much lift, but will produce much interference drag.  Yet, I wonder if this weird triplane will fly properly at low speeds.  Any thoughts?

"Whose front view is shown in the figure" What figure? - Nevermind, seems imgur is having issues this afternoon.

Probably is flyable... do you intend a tail?  Or swept wings?  Or...  ?

It would depend on the relationship between span and separation. The dihedral would be too great on a short-span wing, as drawn, leading to all sorts of issues. Since the separation needs to be more than usual, approaching two chord lengths, you would need a very high aspect ratio, maybe 15 or so.
But if you were to leave out the middle wing and cross-brace each side with thin wires, as a biplane it would be just as stiff and perform a heck of a lot better.

This might work better thinking on the x,y, and z axes.  I am seeing a dihedral upper wing, a straight lower wing, and a t-tail.
A dihedralled upper wing, with a little sweep, would interfere with the lower wing first near the front, causing the plane to pitch down before it stalled if AOA became too great.  There should be some gap between the two.
The concept, as drawn, would suffer from interference issues, and, as the other writer explained, would work far better with bracing wires, better still with 2 or (or 1) thick cambered cantilevered wings.
Also possible would be a "Sopwith Bonanza":  a biplane with a butterfly tail.

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How do I convert my FAA PPL to the equivalent in the UK / Europe?
I am returning to the UK and want to convert my FAA PPL to a UK PPL. Does anyone know the process for doing this?
I am getting lots of conflicting information.

Welcome to the site @EricLacey, there's plenty of questions about going the opposite direction, but none about coming to the UK that I know of. I suggest you contact the CAA and ask. EASA and the CAA tend to be stuffy on these types of things, so while the FAA will issue a license on the basis of a UK one, the CAA will likely make you re-test and pass all the exams.

As a disclaimer, this answer is based on Googling, not on personal experience, and compared to the US the situation seems very complicated. I'd suggest contacting the CAA directly; EASA delegates licensing to its member states, so the practical details depend on the country you're in. You can read about one person's experience here, although it's in Hungary, not the UK.
Anyway, it looks like there are two processes: validation and conversion. A validation is a temporary license valid for 12 months only (or 24 months, according to some sources), whereas a conversion gives you a full EASA license. The purpose of a validation seems to be to let you fly while you work on conversion; I couldn't find any definitive sources on the process.
As for conversion itself, the requirements I found on various sites are consistent with EASA's own information:

If you hold a Private Pilot Licence obtained outside Europe or not
  according to the relevant EASA licensing regulations, you can convert
  it to an European one. In order to do this you will need to pass an
  exam on Air Law and another exam on Human Performance. You also need
  to undertake a skill test and have at least 100 hours as a pilot in
  the relevant aircraft category.

That doesn't sound too bad, although I have no idea how much effort and expense there is in practice. If you're instrument rated, though, the requirements seem quite onerous compared to the US because of the large amount of theory required (this is from the same EASA source):

Competence Based Instrument Rating (CB-IR): This rating is for those
  who already have an Instrument Rating issued outside Europe (e.g.
  FAA). This reduces the requirements of obtaining an Instrument Rating
  to at least 80 hours of theory and 40 hours of instrument time, 25
  hours of which must be training.

And to add more complication, it appears that the UK currently allows FAA license holders to fly using their FAA license but in the UK only, i.e. it isn't an EASA license and therefore not valid across Europe. There's an ongoing discussion with EASA about it, so it might not be a good long-term option but I really have no idea.
There's also something in the UK - and perhaps other countries? - called an NPPL, a National Private Pilot License. But that also has limitations, and isn't valid outside the UK.
Finally, although it's common to see N-registered aircraft in Europe, if you're a European resident then you can't fly them with just an FAA license. You also need an EASA license.
Someone who's actually converted an FAA license to EASA could probably give you a better answer.

This is how you can validate an ICAO licence for non-commercial activities (from the CAA website):
Validating an ICAO licence for non-commercial activities allows you to fly for personal purposes (not for pay) under Visual Flight Rules (VFR) in UK airspace using your ICAO licence.
People with an ICAO licence who want to fly privately, for personal reasons, for more than 28 days a year in UK airspace need to apply.
You need to have:

A valid ICAO licence and medical.
Any required class or type ratings must also be current and valid.
At least 100 hours of flying experience in the relevant category of aircraft.

Additionally:

The aircraft you plan to fly must be registered in the UK, or its operator's main base must be in the UK, or the aircraft must be based or maintained in the UK.
You must pass a licence skill test conducted by an authorised Part-FCL UK examiner.
You must demonstrate language proficiency, which will be tested by a UK examiner.
If you don't have a full ICAO class II medical certificate, you'll need to obtain a UK Part MED Class Two Medical Certificate. FAA Class II medical certificates are not acceptable.
The validation is valid for up to one year. If you want to extend it, you must enroll in a course to obtain a UK licence before it expires. Extension is only possible once and must be done before the expiry.
Refer to Article 6 or 7 of Section 2 (UK (EU) 2020/723) for more details.

Original source: https://www.caa.co.uk/commercial-industry/pilot-licences/non-uk-licences/validate-an-icao-licence-for-non-commercial-activities/

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Why are Israeli planes followed by an armored police truck at ZRH?
While I was actively traveling to Zürich (for three years before Covid pandemic), I noticed that the Israeli airplane is always being followed by an armored police car with a machine gun turret on top. The car moves parallel with the plane all the way during taxiing.
As far as I could notice, no other planes/companies had this security measurement. Does anyone know why is this happening? Are there some increased security risks connected to the planes/passengers coming to/from Israel?

Related: Why don't El Al 747's stay at the gates at JFK?

El Al has additional security at EVERY airport they fly to. The level of security varies, but it is always present.

During the latter half of the 1990s, Tower Air's 747s had the same security precautions at Amersterdam as El Al. Tower was carrying generally as many pax in/out of Tel Aviv as El Al, and being Jewish owned, was considered to be at the same level of risk.

When we were living in Hassia, somewhat near Frankfurt, we would sometimes take a day trip to FRA on a weekend and go to the visitor's platforms and watch the planes. We moved away in 1991, so this must have been 30 years ago or more, and I very clearly remember seeing this even back then, and my parents explaining to me what it was all about (not easy for a 8-10 year old!)

I have witnessed this in many airports over the years, usually this goes hand in hand with planes to Israel been boarded in remote parts of the terminal. Without going into politics Israel is in a long conflict with the Palestinians which is in the heart of many terrorist organizations ideologies.

It is happening as an extra security measure, probably attempting to mitigate the risk of an explosive-laden person or car breaching the perimeter fence - like many city airports ZRH has a multitude of roads running around the perimeter fence which cannot all be manned 24/7. Is it mostly for show? Who knows!
There has always been more risk associated with flying to Israel - anyone who flew there pre-9/11 was not surprised by the extra security measures added to all flights post-9/11 as they had been dealing with them since forever.
It seems that American might also get the same treatment at Zurich based on a photo here: https://www.airliners.net/photo/American-Airlines/Boeing-767-323-ER/531127/L

Funnily enough, the single comment on that linked photo is asking why El Al and American Airlines have that APC driving with them.


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What sort of debris has been found in 737 Max fuel tanks?
There have been numerous reports of Boeing finding "foreign object debris" in the fuel tanks of its 737 Max airliners.
It's not clear what this debris is. It could range from a couple of missing screwdrivers and a blowtorch, to perhaps microscopic particles that might contaminate the fuel.
Has Boeing released any details of what these objects are? And, more generally, how unusual is such contamination?

I saw something that claimed it included tools, shoe covers and dirty rags but I can't remember where.

@Flexo I'm pretty sure that I did too, and now can't find it either, but 1 and 2 (for example) explain that the term "foreign objects" can be used to describe objects like those, and it's possible that reporting or editing glossed over the distinction.

As a generic answer, not unusual. Besides personal objects like bucking bars, clecos, rags and such left in tanks, the biggest contamination source, from my experience working on a production line many many years ago, is "swarf". Swarf is aluminum drill shavings and mountains of it are created during assembly.  You will also get wire cutoffs and other similar bits, shop (bucked) heads of rivets that were drilled and punched out because the rivet was dumped when being driven and had to be removed and reshot.
All that stuff is supposed to be thoroughly vacuumed out before the sealers go in with their goo guns, but nothing is ever perfect.  Even if the wing was cleaned out before the sealing was done, if the wings get modded or repaired farther down the line, where more rivets get drilled out and redone, more swarf or other contam gets introduced and may get overlooked.
The first time fuel flow test runs are done on the completed aircraft, that's when you find out how bad a job they are doing up the line as the fuel screens and filters are removed to check.
Some manufacturers will build special rotation fixtures to put the wing in (not really practical in a one piece swept wing, but easy to do with a straight one) after it comes out of the assembly jig to rotate, barbecue chicken style, while they listen for objects clattering about. It's good for catching bucking bars, clecos and such that get left inside.

Do fuel flow test reveal solid foreign objects like tools that don't emit fibers or particles like some rags might? I want to ask "What's the longest time that a tool has sat in a commercial aircraft fuel tank before being discovered?" but not sure if it's on-topic ;-)

@uhoh I'm not sure whether I want to hear the answer to this question or not. Could be both terrifying and relieving... :)

Those little cylindrical sheet metal clamps that look like spent cartridge casings.

@uhoh no only items small enough to get through inlet screens, maybe 1/8 to 1/4 inch.

They'll do an initial fuel flow test, using a special test rig, to flush out the system and check for leaks.  All the filter screens are pulled and inspected, cleaned and reinstalled.  They repeat this until the the screens are clean after a FF run.  None of that stuff will actually make it into a pump or an engine, but if severe enough it could block an inlet or filter screen causing low fuel pressure indications.  Things like bucking bars or other larger inanimate objects are fairly harmless because they'll just sit there taking up space in a corner of the tank (notwithstanding rust issues).

@BenCrowell Cleco Pins are temporary fasteners used to hold metal together as it's being riveted. The piece is clamped in place, then holes are drilled for the rivets. As each hole it drilled, a Cleco pin is put in place to keep the pieces from moving. They're left in place until each one is replaced by a rivet.

I saw this yesterday:
Samchui.com: Foreign Objects Discovered In Boeing 737 Max Fuel Tanks

Included in the list of items discovered are rags, tools, metal shavings and other production equipment, which pose a serious safety risk in flight and on the ground in operational service.

I added a quote from the story, because link only answer are not considered a good practise here.


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Can all airborne aircraft be stored at their origin or destination airport?
With the progressing outbreak of the Corona Virus the IATA has recently changed its predictions about the losses to be suffered by the aviation industry

The losses originate from the reduced number of passengers and the subsequent grounding of aircraft for which there are no passengers.
The question is, can all the aircraft in the air be grounded at either their origin or destination airport. If not, where else can they be stored?

Most aircraft are on ground at night

Not if I look at FR24 as it is always somewhere around the world night. Right now the sky looks very busy in Asia and Australia.. Smaller jets maybe stay on the ground but all the larger aircraft are still flying

You probably want to look at what happened in the US after 9/11

The number of passenger aircraft airborne decreases during the night. The number of cargo aircraft increase during the night. And, night is relative to the longitude of the area at which you look. Long haul flights typically do not necessarily correspond to this trend. And, there seems to be more long haul flights over the Asian land mass than there is over the US land mass. Your typical US airfield, scheduled carrier or GA, is a veritable parking lot after midnight.

Freight will keep flying, regardless.

You really need to clarify what you're asking about:  All aircraft?  (And why would the corona virus keep me from flying my Cherokee?)  All commercial aircraft, which is only a fraction of all aircraft?  Or all passenger aircraft, which is a smaller number still?

As the question will still be valid in several years, you may add dates when speaking of "recently". Yes it can be deduced from other metadata but it is more readable if it is included directly in the question description.

Short answer: Yes.
You need to distinguish between short-haul and long-haul fleets.
For example, when it is 4 a.m. in Central Europe, almost all the aircraft which fly short-haul routes throughout Europe during the day will be on the ground somewhere in Europe simultaneously and there must, therefore, be ample parking for all those aircraft (though not necessarily at gates). Similarly for other parts of the world: when it is 4 a.m. in the central U.S., all the short-haulers will be parked-up somewhere in the U.S.; when it is 4 a.m. in South East Asia, all the short-haulers will be parked-up somewhere in South East Asia, and so on. There must, therefore, be ample parking for all short-haulers globally.
For long-haul fleets, it is a different matter. Such aircraft spend up to 16 hours a day in the air, and therefore well over half the aircraft will usually be airborne at any one time, round the clock. It is highly abnormal to have all long-haulers on the ground simultaneously. If all those long-haulers need to suddenly be grounded, it can cause serious problems, as happened after 9/11 when the entire transatlantic and transpacific fleets suddenly stopped flying. However, even then, the airport operators did manage to find sufficient parking.

When nothing is flying, runways can be used for parking. (Not every runway, obviously, but some of then.) The runways at airports the long-haul jets typically use are roughly 2 miles long, which is a LOT of concrete. And they tend to have the in parallel.

Note that there are LOTS of aircraft which never visit a gate, and which might (if not flying) be parked on the ramps of FBOs, or at cargo terminals.

it's always 5 o'clock somewhere :)

Most FedEx, UPS, etc cargo aircraft are on the ground or in the air at (more-or-less) the same time for the particular continent they serve. The handy thing is that their ground/air cycle is more-or-less opposite that of the pax fleet.

Possibly not at the origin or destination, especially if the grounding is sudden and unbalanced as happened after 9/11. Hub airports may not have enough pavement to hold all outbound and inbound planes; it's assumed only half will be there on average.
However, with a modicum of planning or if ferry flights are allowed, both of which should be true in the case of something relatively slow-moving like an economic downturn or pandemic, then aircraft can be moved as needed to places where parking is cheaper and/or more abundant. Consider how airlines managed to find plenty of places to stash all the grounded 737MAX planes in a matter of days.
If the impact is severe enough, planes can be parked on extra runways, such as sometimss happens when a huge number of business jets converge on an airport for a major sporting or political event.


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What would the "wings level" button most likely do if activated in the event of a flat spin?
If an aircraft equipped with a wings level button (such as the TBM 930) entered a flat spin, would pressing it accomplish anything productive?
I am aware that the purpose of the button is to return the aircraft to straight and level flight if the pilot becomes uncomfortable with the vehicle's orientation. However, what I am unsure of is whether this system can control both the engine and control surfaces in a manner that would be potentially helpful in a seemingly unrecoverable situation.

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text:
How much do the fan blades of a GE90-115b stretch when the engine is spinning at maximum RPM?
I've always wondered what kind of stresses and resulting deformations jet engines are subjected to when running.

@FreeMan My apologies. I added "fan blades" to the title in order to clarify, after Notts' comment. Thanks!

I don't know the exact answer, but it's on the order of 0.100" (i.e. it's more than 0.010" and less than 1.00").  The more interesting part is that it's not just a simple linear stretching. The blades have a twist to them, and at speed they untwist, which is a strong contributor to the total change in length from 0 rpm to redline.


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Why paint a British roundel on a non-British Lynx?
In recent years, some of the Westland Lynx helicopters of the Portuguese Navy have undergone some form of mid-life update (MLU) in order to have their engines and avionics upgraded. Also, allegedly, a few Portuguese naval aviators have undergone training and qualification on these updated Lynx helicopters.  Allegedly, such work took place at Leonardo's site in Yeovil, Somerset, England, United Kingdom.
Interestingly, articles on the aforementioned events do display photographs that show a British roundel alongside a Portuguese roundel on Lynx helicopters of the Portuguese Navy. The following photograph shall corroborate my claim.

Question
Why would one paint a British roundel on a non-British Lynx?
At the moment, only one hypothesis occurs to me — though the aircraft being upgraded do belong to the Portuguese Navy, the test pilots are British.

References
On Portuguese Lynx helicopters with British roundels:

Marinha Portuguesa, Helicóptero da Marinha Portuguesa realiza primeiro voo após processo de modernização, 18 de fevereiro de 2020. [Google's Portuguese-to-English translation]

First flight for upgraded Portuguese Lynx (2020)

Portuguese pilots in UK for Lynx Mk95A (2020)

On Brazilian Lynx helicopters with British roundels:

Leonardo: upgraded Brazilian Navy Super Lynx makes successful maiden flight (2017)

Third Wild Lynx for Brazilian Navy (2019)

Brazilian Navy completes Super Lynx Mk21B acceptance (2021)

Best guess; the photos are from the delivery flights in the 90s. The helicopter in the photo has the same registration as when it was first delivered (ZH583) and has not been active since.
Update: Although I'm having problems finding an authoritative source, it looks like the registration was resurrected for test flights post-upgrade. Mark Youd has taken a few photos of ZH583 recently(flickr), it was listed in the April update from a site called "Military Aircraft Markings" and looking at various planespotter forums and various flight tracking sites(1)(2) you can find multiple reports of flights being undertaken using the original ZH583 registration.
The roundel and registration is temporary and easy to remove, but was required for the test flights in the 90s as well as prior to delivery post-upgrade. Looking at other photos you'll see the Portuguese registration on the tail; on your photo this area appears to be covered up to avoid having an aircraft with two different visible registrations during test flights.
As for your hypothesis; the second is totally off target. There are loads of barriers in place to avoid having any situation involving a trigger-happy fighter pilot, such as predefined rules of engagement and procedures civilian and military control centers follow.
My guess is that the first one is closer to the truth; although I haven't found a source for it, I can imagine that it would be easier for the factory and the test pilots undertaking the upgrade and test flights to schedule and log flights using the UK registrations.

Like (Brazilian) ZH962, export Lynxes (Linces?) underwent test flying e.g. at Yeovilton and would have needed British military serials.


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Why do pilots refer to the Flight Service Stations as "Radio" in the the United States?
When using an aircraft radio to call a Flight Service Station ("FSS"), why do pilots refer to them as "radio?" I understand calling control towers "tower", ground control "ground", Air Route Traffic Control Centers ("ARTCC") "Center", and so on, but why "radio" for a Flight Service Station? Why isn't it "Station?"

I suspect it is a holdover from the early days, “The beginnings of FSS date back to the World War I era, where radio operators assisted air mail pilots flying across the US. In addition to weather functions, they also assisted with a basic form of Air Traffic Control. As aviation grew in the 1920s and 30s, these radio operations expanded and made their services available to any pilot who requested it. Fast forward to 1960, shortly after the creation of the FAA, and the first Flight Service Stations were unveiled.”  http://studentpilotnews.com/2014/02/10/flight-service-stations-fss-can-think/

@JScarry I suspect you are correct. I would love to hear form some old-timer pilot or FAA employee to give us the back story on this. I might need to call my 90+ year old primary flight instructor to ask for the scoop.

I guess they are just "radio", with no authority to give clearance whatsoever.

Well, the answer to why pilots call them this way is because the regulations say we must - but that's not your real question.

@DanHulme good point! We call them that because we were told to call them that. As you eluded, the real question is where did "Radio" come from, all the other names make sense. I guess there aren't many old timers on here.

"Radio" is just a shortened version of "Aeradio Station" which was the term used before "Flight Service Station".

Was it referred to as Aeradio within the United States?

Whether it is or not, "X Radio" is also the correct form in the UK and Eire (possibly other places too), so the origin might not be US-specific.

Generally the use of "Radio" in the station callsign has come to indicate the absence of radar control.
For the official word, here are relevant Glossary entries,
From FAA's AIM:

From ICAO Doc 9432 (Manual of RadioTelegraphy):

"Radio" is the default suffix for all ground radio stations; there are many other standard suffixes (e.g. Ground, Tower) that are used instead when they apply, but there's not one for FSS, so they're stuck with the default.
Note that each country can organize their ATSUs how they see fit, and the way the US has split FSS into something separate from ATC is unusual, perhaps even unique, which is why there's not a standard suffix for it.


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What follow-up actions, if any, does the FAA take when a pilot declares an emergency in flight?
This question focuses on what the FAA is required to do when pilot declares an emergency, as opposed to what a pilot is required to do. (The answer to this question is not covered in typical pilot training).
Example: Pilot loses situational awareness and becomes lost. Pilot is low on fuel and declares emergency and ATC provides vectors; pilot turns towards nearest airport. Pilot arrives at airport and makes an uneventful landing at small airport. No other traffic was diverted, aircraft and passengers fine, pilot did not deviate from any Part 91 FARs.
After the emergency is over, what legal, administrative, or investigative actions will the FAA or other official bodies take?
I understand that when a pilot declares an emergency the pilot gets priority from air traffic control, and may take reasonable actions for the safety of the flight even if it means deviating from part 91 regulations.
It would appear that, so long as there was no incident or accident, no one is injured, and no regulation is broken that FAA will take a "no harm, no foul" approach.
I'm curious if any one has source information as to what should the pilot expect: a call from ATC, an investigation, nothing, etc.? (Assume no FAA deviations, no injuries or accidents, etc.)

After a successful landing that did not involve any deviations, the pilot can reasonably expect, "Good landing. Turn next taxiway, contact ground, G'day"

@abelenky that is my intuition also. If you could provide a little backup or rationale there is a little green check-mark in it for you. :)

I would, however, assume the NTSB wants to figure out why the engine quit.

@JörgWMittag excellent point! I'm changing the example. Thanks!

@JörgWMittag It might seem strange, but there's no requirement to report an engine failure to the NTSB unless something more specific happened, e.g. an uncontained turbine failure or in-flight fire (see 49 CFR 830.5). Even in a large, multi-engine aircraft, you only have to tell the NTSB if two or more engines failed.

I cannot vouch for anything the FAA may be required to do, but I can vouch for Abelenky's comment:  After being told on downwind abeam the approach end of the runway, (vapors in the tank after being diverted when my flight lead blew a tire on the runway of another nearby airfield...) to follow a C-130 on DEEP straight in final, I flipped the squawk to 7700, started my approach turn, and told my right seater to announce emergency fuel and our intent to land as soon as the chatter broke.  We were cleared immediately, and it ended as described above.

I don't know the FAA policy, but normally, you don't report deviations from the regs, unless asked to.  I have declared emergencies, gotten priority handing in the DCA area, and a variety of eyebrow raising events over the years.  However, the FAA has never asked me to submit a written report. Once or twice, I have gotten a call from an operations inspector, and answered their questions, and that was all that became of it.
In general, if you had a bad day, don't tell about it. Just get on the ground safely, and be polite to people, and hope that you don't have any further review.  Of course, you must comply with NTSB 830, but if you are required to do that, you have had a really bad day, and might want to get some help (aviation attorney).

It is FAR 830, not NTSB. Here is the section if people want to look it up https://www.ecfr.gov/current/title-49/subtitle-B/chapter-VIII/part-830/subpart-B/section-830.5

@RowanHawkins, you are correct.  However in the last 5 decades it is my experience that it is commonly referred to by pilots and CFIs as NTSB 830, rather than 49 FAR 830.

The FAA will most likely not take any type of actions dictated by the department itself until after the emergency has taken place. ATC is considered a division of the FAA yet still, they are the ones who are taken the responsibility from the time the emergency was declared to when it has been dealt with/ended. After the incident, the FAA may process an investigation along with the NTSB, though the primary reason the FAA exists is to create standards and regulation for modern aviation and such emergency procedures. The pilot should expect a call from ATC who will guild them to the safest solution possible and will deal with any other parts of the emergency that may arise.


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Definition of "Rotation Speed" vs "Lift Off Speed" vs "Fly Off Speed"
Is rotation speed and lift-off speed ever used interchangeably? (AMENDED Question) Is lift off speed and fly off speed the same? (See supplemental info below)
I thought I clearly understood the difference between these two terms:

Rotation is the point at which the longitudinal axis of the aircraft is "rotated" about its lateral axis from a horizontal orientation in order to increase the angle of attack of the wing.
Lift-off is the moment when the aircraft is no longer in contact with the surface (i.e. ground or water).

However, I was reading something the other day where the two terms appeared to be used interchangeably, which I accepted at first, but now its bothering me. It was a POH and it said that for normal take-off rotate at 70-75 KIAS. However, the POH also says that the "Normal takeoff distance in Section 5 is based on lift off at 65 KIAS."
Found it, here is the text:

So to get the Normal takeoff performance, you can't use normal takeoff procedure?
By the way, after further reading of the POH, I don't think the "lift off at 65 KIAS" is a typo. See the maximum performance takeoff which says to rotate ASAP and "fly off" at 61 KIAS the single engine stall speed of the aircraft. (See Copy Below).
I think they were just hard-core back then. So this raises another terminology question "fly off" speed. So we have rotation speed, lift off speed, and fly off speed. My interpretation is that for max performance takeoff rotate ASAP, if airplane flies below 61 KIAS, then keep it in ground effect until 61 KIAS, then fly off.

What aircraft is this for? It may be a typo in the documentation and would help to cross-reference another POH.

@RonBeyer It's for a 1978 Grumman/Gulfstream Cougar GA-7. However, even if the speed is a typo, I'd still like to know if "rotation speed" and "lift off speed" are used interchangeably. I consider them two distinct events.

Your original understanding is correct.  Rotation speed and liftoff speed are two different things, the former being the speed you are to make an input, and the latter the speed at which you get a result (weight off wheels).
That's almost certainly a typo and is supposed to say 75kts (my guess), which would be the demonstrated maximum distance to weight-off-wheels with rotation initiated late in the 70-75 kt range. Manuals published as integrated handbooks like that tend to never get revised unless a new edition is published, and the Cougar was only in production for a couple of years making a little over 100 aircraft, so I'd be surprised if there is a newer edition than the 1978 one, especially if it involved publishing a new handbook over a minor typo on an out of production airplane.
On a light aircraft the input and result are just about instantaneous and a rotation initiated at 75kt will result in a liftoff pretty much at 75kt or maybe a knot or two higher.  On high performance aircraft rotation speed and actual liftoff may be 1 or 2 seconds apart and it's more obvious that they are different things.

Light aircraft often sit slightly nose-high, so they don't need much rotation. Larger aircraft on the other hand always sit nose-level (floor-level, for easier loading), but cruise slightly nose-high (so they are not nose-low even when empty), so the difference between ground and take-off attitude is larger.

I believe that your interpretation of rotation and lift-off is correct.  The POH is basically saying that minimum control speed is 61 knots, minimum lift-off speed is 65 knots, and recommended rotation speed is between 70-75 knots.  The POH is saying that the performance charts in section 5 are based off of lift-off speed of 65 knots rather than the recommended 70-75 knot lift off speed.
It is usually a good idea to rotate at an airspeed higher than the minimum lift-off speed.  That is why the POH is recommending the higher rotation speeds.  Remember that you will need some extra airspeed to break out of ground effect. Also to avoid vertical obstacles at the end of the runway accelerate to Vx which is listed as 81 knots in the POH.
Also for pilots like myself who take off at airports with gusty wind conditions it is a good idea to build up extra airspeed before rotation so that the plane won't sink back to the runway if the wind suddenly stopped or changed direction.
I usually rotate at Vx everytime.  While doing this uses a little more runway I do have better climb out and control authority on lift-off.  Since my airport has 7000 foot runways I still have plenty of runway if something goes wrong and I have to land straight ahead.

This FAA document, part of a larger document, the Airplane Flying Handbook, discusses rotating and liftoff on page 5-5
https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/airplane_handbook/media/07_afh_ch5.pdf

When all the flight controls become effective during the
  takeoff roll in a nose-wheel type airplane, the pilot should
  gradually apply back-elevator pressure to raise the nosewheel
  slightly off the runway, thus establishing the takeoff
  or lift-off attitude. This is the “rotation” for lift off and climb.
As the airplane lifts off the surface, the pitch attitude to hold
  the climb airspeed should be held with elevator control and
  trimmed to maintain that pitch attitude without excessive
  control pressures. The wings should be leveled after lift-off
  and the rudder used to ensure coordinated flight.

So one could say you rotate the plane at one speed to bring the nose up, and then some finite speed later the airplane will lift off. A properly trimmed airplane will often just lift off the runway with no elevator input needed. Such a plane will sit on its gear in the liftoff attitude.

I have a problem with that one.  Don't know of many airplanes that will generate enough tail downforce to lever the CofG over the main wheels at rotation speed with the trim set to the normal takeoff range.

It sounds like the handbook is using the two terms interchangeably. It says, "As VX approaches, the pilot should apply back-elevator pressure until reaching the appropriate VX attitude to ensure a smooth and firm lift-off, or rotation." In another part of the handbook it says something simply "lift-off, or rotation" as if they are the same thing.

Cessna Cardinal will fly itself off the runway.


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Is the "auto-routing" created by online flight planning resources preferred by ATC over Direct routing when NO preferred route exists?
I noticed that when I use online flight planning resources, they provide an "auto-routing" option for my flight. I also noticed that they are the same between both services so it seems like both are pulling the route from somewhere. Additionally, the auto-route appears to be different than a "preferred route" because, for example fltplan.com will say "No Preferred Routes or Stored Routes" then it gives me (a sometimes crazy) auto-route.
Are auto-routes predetermined or is it just an algorithm (i.e. nearest intersection/victor airways to destination)?
Extra Credit Question: If there is no preferred route for a given destination, is filing Direct or using the auto-route more likely to get you a "cleared as filed?"

I'm voting to close this question as off-topic because it asks about particular flight planning services and their features, rather than about aviation per se.

Seems on-topic to me, the auto-route principle is general enough

The people using those sites generally won't be up in the flight levels where probably 80% of the traffic is, so it's hard to see how ATC would care one way or the other.

I did some follow up research and also spoke to an air traffic controller and I have a partial answer to this question.

If the "auto-routing" doesn't make much "sense" and there are no "preferred routes" then the probability of "getting a direct clearance would be fairly high."
The "auto-routing" logic is simply using nearest victor airways from Point A to Point B. (I'm still looking for a source for this, but it seems pretty obvious to me now).


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Why "Throttle...Open 1/2 travel" on engine troubleshoot checklist?
Why do some engine troubleshoot checklists (on small single engine piston aircraft) call for throttle to only be open 1/2 travel? I suspect it has something to do with modern fuel injected engines, but haven't found anything explaining why half throttle, instead of full throttle.
Below is an example, however, I saw at least one other checklist online for another single engine piston (non-Cessna) that had similar "1/2 open" throttle language.

Troubleshooting what?  Flooding?

Is this an in flight check list or on ground?

The tags say engine failure, but the question doesn't make that clear.

Can you copy and paste a specific checklist, to make sure we understand what you're asking?

@Pondlife see screenshot. I saw another checklist online for different SEL piston aircraft with same 1/2 throttle language, but couldn't find it again. This appears to be the checklist for partial or total engine failure, presumably in-flight, not engine failure on take-off.

"Modern fuel-injected engines" are rare as hens teeth in light, GA aircraft. See the (approximately) 1,843 questions here as to why.

Revised following update to OP:
If the engine quits and you're gliding along with it windmilling and the throttle pulled back to idle, if it comes to life at some point, you may not even be aware of it because you can barely tell the difference between off and idling when it's windmilling in a glide.  On the other hand, pushing it full forward isn't such a good idea either.
You want it set to a power setting that makes it obvious it's come back to life, but you don't want to set it to full throttle because you don't want it going full bore instantly, which is generally not helpful to the engine because the oil pump may only be making 20 or 30 psi while windmilling, or none at all if it stops windmilling, and full power before the oil pressure can catch up is murder on the plain bearings of the crank journals that depend on oil pressure to keep crank journal and bearing separated from physical contact.
So half throttle makes a nice compromise.


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Could an AN/APG-79 AESA radar "lock-on" a single bird?
Could a fighter pilot in 2015 using an AN/APG-79 AESA radar "lock-on" a single bird?
I know that modern radars like the AN/APG-79 in modern combat aircraft like the F/A-18F filter out false alarms with Doppler processing and use what could be called "filters". Could an F/A-18F pilot "lock-on" a single bird using STT (Single-Target Tracking) mode or by using any other radar modes?

Just for clarity, are you asking about literally birds, that is, living avian creatures with feathers and typically the ability to fly or at least soar under their own power?

Yes, I am talking about a biological.

You are aware that the full capabilities of a military system such as this are generally classified and unavailable to the public?

Yes, of course, DOD clearance must be "secret" but this is an hypothesis "bird" that has been proposed for this event, so I am investigating this possibility  : https://www.metabunk.org/go-fast-footage-from-tom-delonges-to-the-stars-academy-bird-balloon.t9569/

Depending on the radar, the accuracy fallow might be too big for a smaller object as radar resolution and accuracy matter a great deal in detecting and hitting a small target, that is why usually birds do not show up on radar or are actually filtered out as they could not hit targets that small anyway…
Resolution refers to the size, meaning electromagnetic size or radar cross section (RCS), of the objects a radar can detect. The smaller the minimum detectable RCS of a radar system, the better its resolution. A radar with poor resolution might see a supertanker sailing past but not a tugboat, for example.
Accuracy is referring to the degree of uncertainty in the radar’s calculation of the target’s location. A very accurate radar, for example, might tell you that it’s detected a target at a distance (range) of 87.118km ±10cm from the radar antenna. A much less accurate radar seeing the same target might report its range as 90km ±100m.

Welcome to Av.SE!


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What happens when an aircraft type is grounded while in flight?
Over the past few days, many countries have decided to ground the 737 MAX. Among these, several have also decided to deny passage to the affected models through that country's airspace. How does this affect flights which were already in the air at the time of the announcement, typically? I can see several options:

The flight returns to its origin, fuel permitting
The flight lands at the closest viable airport in the destination country if fuel is insufficient for a return to origin (minimizing the amount of time in the destination country's airspace)
The flight proceeds to its destination airport as filed, even if this means spending several more hours in the destination country's airspace than the second option
The flight proceeds to the closest viable airport regardless of whether that airport is in some third country being overflown (although I can foresee this causing immigration/visa/customs issues for the passengers)

I'm assuming that (1) is commonly used, given the flight paths on internet flight trackers yesterday, but which of the other options are rooted in reality?

The FAA is currently dealing with that on the 737 MAX.  They are allowing any airborne 737 MAX to continue to its destination or to an alternat or emergency landing site at the discretion of the crew  within the US thence flight ops are prohibited. Special airworthiness certificates and ferry flight permits may be issued by the FAA for moving the aircraft to a home base or maintenance depot as the discretion of the Administrator.


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Are there any non-bureaucratic hurdles preventing more widespread adoption of synthetic vision?
Occasionally, a flight will encounter bad enough weather that the crew will become disoriented. While tools like a terrain radar, ILS, and GPWS/TAWS do help the pilots regain orientation, they're not universal; some aircraft aren't equipped with terrain radar, ILS only works on approach to runways supporting ILS, and GPWS is pretty coarse and primarily aural, not visual (beyond a flashing warning sign) on most aircraft. This means that there's still a risk of overshooting or undershooting a runway, or even controlled flight into terrain.
Some higher-end private aircraft have started incorporating decked-out glass cockpits which, among others, can include synthetic vision systems -- these can show terrain, glide slopes, and other traditionally VFR elements which can otherwise be invisible during night flying or in poor weather.
I haven't seen high adoption of these kinds of systems even in brand-new airlines, though; is there a technical reason why these aren't being included (or even mandated) above a certain type rating? Is it purely pragmatism while the system becomes more ironed out? Or are the hurdles before adoption purely bureaucratic at this point?

Is money a non-bureaucratic hurdle?   Even the cheapest glass-cockpit can run $15,000.   iPads and portables may have synth-vision, but are not certified.

Well, there are no bureaucratic hurdles. The bureaucracy is not there just for sake of it, it is there to make sure the risk analysis was properly done and all problematic cases are handled. After all, synthetic vision is only as good as the data it has and now your life depends on it.

The question makes flawed assumptions about SVS. EGPWS is not "primarily aural", all EGPWS systems have a terrain display, and new aircraft have a profile view. SVS does not involve any new sensors, all you're seeing is the existing EGPWS terrain display and glideslope being rendered in 3D. The question is whether this eye candy really enhances safety, especially in IFR operations, or just there to sell big bucks avionics suites.

It's not bureaucracy in the sense of pointless red tape, it's the demands of certification for brand new systems on Transport Category airplanes.  The hoops that have to be jumped through are epic. Engineering standards, testing this, testing that, covering every conceivable possibility (or trying to).
You always see new innovations in GA, then Corporate, then Transport, because that's the certification difficulty ladder imposed by the demands of having to achieve near perfect safety with a better than one in a billion risk of a catastrophic crash due to a component failure.  (Airliners are, by a far, far margin, the safest way to get form A to B aside from an ox cart - there hasn't been a crash of a heavy in the US in, what, almost 20 years now?)

Maybe not a passenger heavy, but the recent Atlas crash is a common passenger type. I'd say the streak is broken.

Well yeah but I'm just referring to pax heavies in the US.  There was a 737 crash in the Canadian arctic about 7 years ago due to some unbelievable incompetence by the Capt and a not sufficiently assertive FO, but that's the only crash of a passenger heavy in North America since 2002.  Quite a feat.


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Why is China still heavily reliant on Russian turbofan engines?
According to Paul Schwartz, China is "still heavily reliant" on Russian turbofan engines:

Beijing is still heavily reliant on Russian aircraft engines, however, due to the great difficulty of reverse engineering advanced turbofan engines. Thus, additional purchases in this area remain likely as well. [...] The purchase of additional Russian turbofan engines will allow China to continue building out its military transport fleet, while keeping its J-10 fighters and H-6K medium-range bombers operational. The J-10 is an important component of China’s air force, while the H-6K allows China to conduct cruise missile strikes out to the second island chain.

Source: Paul N. Schwartz, The changing nature and implications of Russian military transfers to China, CSIS, June 21, 2021.

Why is China "still heavily reliant" on Russian turbofan engines? Why is reverse-engineering advanced turbofan engines so difficult? Is it due to lack of expertise on

materials and metallurgy?

precision machining technology?

control systems?

electronics?

China is an industrial powerhouse.  Naively, one would expect China to be ahead of Russia on all fronts, but that is not the case, which piqued my curiosity. I know that, in recent years, COMAC faced difficulties but it is alleged that those were of a structural nature, not quite turbofan-related.

Related:

Countermeasures taken to prevent reverse engineering of military fighter jet technology?

Sometimes it's cheaper and easier to simply buy the complicated bit from a friend than bother producing it in house. The Chinese air force is still heavily reliant on Russian aircraft and engines tend to burn out faster than airframes so the need to replace them rapidly vs replacing airframes tends to be much higher. All of the air superiority aircraft that China operates are either Russian built or Russian designed so why not use Russian engines if they are willing to sell them at a reasonable price?
Forget about designing new engines, even building existing designs takes high quality metallurgy and manufacturing techniques that China may simply have not mastered yet, or again, is unwilling to invest in mastering if Russia is willing to be a partner.
This article provides a decent overview of the situation while this article indicates that they are indeed beginning to build domestic engines for their fighters and there seems to be continuing development. Keep in mind this only begins to put china in league with production of jets like the F-22 that the US has been building for the better part of 25 years.
Its also worth noting that the ability to build something and the ability to understand something are very much not the same thing and there is skill required on both fronts to master something. Even if China were able to spool up the ability to build Russian designed engines they would also need to spin up the academic side of the equation to advance any designs they were building and avoid being stuck with out dated designs.

Side Note: It is not uncommon through out history to source parts and materials from other places for wartime equipment, perhaps the most wild example is that the SR-71 Blackbird used during the cold war to spy on Russia was built mostly out of Russian Titanium...

The short answer is: Designing good and/or efficient jet engines is incredibly difficult, and the Chinese do not have the capability to do so.
Modern jet engines are a marvel of engineering. Some even say that these are the most complicated machines ever built by mankind (on the other hand, some people say that about computers...), see also why do new jet engines cost billions to design. These are very complicated machines, which have to withstand extreme pressures and extreme temperatures. To make them more efficient, you typically have to further increase engine temperatures and pressures. All of this is very design intensive. There are only a couple of high-tech companies which can design those aircraft engines, and the Chinese are apparently actively trying to espionage these (note that they only tried to spy on companies which were involved in designing the engines). I even heard one story, in which an Airbus A320 "vanished" in China to reverse engineer the engines. Only after diplomatic pressure was this aircraft released. However this might be a tale, I cannot find a source for this story.
Therefore long story short, the Chinese simply do not possess the capability to design these engines. And this is due to the challenges of the engines such as metallurgy, aerodynamics, vibration, integration and so forth and so on which is just very hard to master. Western and Russian design companies themselves built these capability over a long time and are typically very high-tech companies such as GE Aviation, Rolls Royce and so forth and so on.
P.S: Some people view Russian engines as inferior to western counterparts though that might not always be correct (How do contemporary Russian jet engines compare to western ones)

I would guess that the A320 vanishing in China is probably a tall tale unless this was decades ago. China has hundreds upon hundreds of A320s (as well as 737s, which use the same engines) in the fleets of its own airlines and even has a factory that builds A320s. It would have no need at all to steal one in order to reverse engineer the engines. As far as the link at the end, that seems to mostly be comparing Soviet-era designs, which really doesn't say much at all about the state of things 30 years later.

According to Abraham Mahshie, the cause of such dependence is the lack of tacit knowledge:

China is still lagging because Russia withheld advanced secrets. China’s struggle in this area isn’t due to a lack of resources devoted to the effort but a lack of domestic expertise, he said.  Many of China’s scientists, engineers, designers, and production managers are in their late 20s and early 30s, and they lack the know-how that comes from apprenticeship programs and decades of specialized experience. To make up for that, China has contracted Russian specialists to work inside Chinese factories.  However, “This isn’t a ‘throw money at the problem’ solution,” he said.  “What they still have yet to understand is, modern aviation engines, particularly supercruise fighter engines, are more art than science,” Markov explained.  Engine workers at producers such as Rolls-Royce, Pratt & Whitney, and General Electric have “tacit knowledge” that the Chinese are still lacking, he added.  “There’s a lot of phenomenology that takes place in an engine that we still do not … understand … with our qualitative computing technology,” Markov explained. “But there’s a guy named Joe who works at Cincinnati Milacron, who’s been working that thing for 30 years, [who] just knows, through experimentation, time, and experience, that you do this thing to make the engine get this outcome. And that’s the part where China just doesn’t have that capability yet.”

Source: Abraham Mahshie, Dependence on Russian aircraft engines could prompt China to ‘fix their … problem’, Air Force Magazine, May 19, 2022.

Bold is mine.

The most likely reason is that the Chinese do not have the technology to be able to duplicate what they see. Being able to measure every dimension of a fan-blade only gets you half-way towards making one of your own - the metallurgical processes are extremely complex not to mention difficult.
Designing a new engine based on an existing design is easy in comparison, but specifying any part to be a little bigger/better/stronger than a part that you cannot even make is pointless.


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What were the rules for logging "simulator" instrument time in 1994 (non-full motion)?
Long before the FAA updated the rules of BATD, AATD, FFS, and FTD, what were the rules for logging simulated instrument time in a synthetic trainer?
Specifically, this question came up, an older pilot had a few log book entries for simulated instrument in a Curtiss-Wright P.3 simulator and it was logged as "simulated instrument", "synthetic trainer" and "total flight time." Nowadays, you do NOT log instrument time in a simulator (unless its full motion) as "total fight time", but how was it logged back in 1994? This person's log book entries were logged by an instructor/simulator operator, and the entry was signed off by the instructor. I looked it up and the Curtiss-Wright P.3 was used by airlines to do instrument training, but I couldn't find anything on how that time was appropriately logged back in 1994.
I imagine back then it may have been appropriate to log it as flight time, but I can't find anything that old that says anything one way or the other.
UPDATE: I found AC 120-45A issued in 1992, which described Airplane Flight Training Device Qualifications. Section 14 of this AC said that Previously Approved Flight Training Devices are essentially grandfathered for 5 years from the date of that AC in 1992. So if the Curtis-Wright P.3 was previously approved as a flight training device then, it would be grandfathered. So, if anyone knows if the Curits-Wright P.3 was ever approved as a flight training devices, that would be helpful as well.

This answer is somewhat non-responsive but may be helpful.
In the 70's I utilized training devices, both in preparation for an instrument rating, and for currency. The training device had a plotter and would tract the path flown.  As I recall it was a regulatory requirement that a CFII or an IGI (Instrument Ground Instructor) provide training for all simulated time.  It was logged as simulated instrument time, and instrument instruction received.
Simulator time on the device was not acceptable for any ratings or currency, unless an instructor was present and endorsed the logbook or other record.
As I recall, two inspectors from the FSDO also used this facility.
When I accomplished my instrument airplane rating and my CFII airplane rating, there was no concern either from the DPE who conducted the instrument checkride, nor from the DPE and operations inspector who rode along on my CFI instrument ride.
I will amend this if I am able to dig out the guidance at that time, which as I recall was not an AC, but rather a collection of Letters of Determination from FAA Legal.

Did your instructor log that time as Total Flight Time in the last column of your logbook? The P.3 sim is just like you described, huge silver cockpit with an operator station on the side with a plotter that would trace a line on graph paper. It was high tech back in the day. I know its legit for simulated instrument time, but was it also logged in the Total Flight Time column? I'm curious if you still have the log book maybe you can take a peek.

Not logged as flight time.  I had a IGI and did not log it as flight time with that rating, or with my CFII when I received that rating.  I provided about 1500 hours of training in a flight training device back then, and always logged it was "simulated IMC" with the N and category / class entry being the simulator model and serial.

Thank you! That is very helpful.


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Is it permissible to log an instrument approach for purposes of IFR currency in a non-IFR certified aircraft?
Assume you maintain VFR at all times and you have a qualified safety pilot on board. Can an IFR rated pilot fly practice approaches under the hood (view-limiting device) using an aircraft that is not IFR certified, and log these approaches for purposes of meeting his/her IFR currency?
Assume the aircraft has the required equipment for the approach (i.e. VOR for VOR approach, ILS for ILS, etc.).

As long as you remain VFR then the equipment requirements for the airplane and the flight are VFR.
§61.57 says “Within the 6 calendar months preceding the month of the flight, that person performed and logged at least the following tasks and iterations in an airplane, powered-lift, helicopter, or airship, as appropriate, for the instrument rating privileges to be maintained in actual weather conditions, or under simulated conditions using a view-limiting device…”.
It doesn’t say anything about having an IFR certified airplane or having a current pitot/static and altimeter check. If you are maintaining SEL IFR currency, then all you need is a SEL airplane. MEL IFR, then a multi-engine plane, etc. And if you are missing some of the 6-pack instruments, all the better for practicing partial panel.

Thats good to know. So you can take the little C152 up with a single VOR/ILS, at half the price, to shoot some VOR and ILS approaches instead of the complex IFR aircraft, with all the glass, and save a couple hundred dollars.

@Devil07 Sure. But the C152 is probably IFR capable—although not necessarily current. There aren’t that many legacy airplanes that are not able to fly IFR. Some of the newer sport planes have a certificate that is VFR only.

I suppose one could assert that, if the airplane is type-certificated for IFR and IFR certified in terms of the transponder, then that would be fine. Assume a qualified safety pilot of all answer scenarios.
If the aircraft is not type-certificated for IFR flight, but has the appropriate equipment and operated in VMC, then that would also be fine.
If the aircraft does not have the appropriate equipment (Say you are trying to fly LNAV approaches using a VFR-only or portable GPS, or using such equipment as a non-legal substitute for appropriate equipment) then that would not be OK.
BLUF: If you're using the proper equipment in the proper conditions with a proper safety pilot, it should be OK. remember that all practice approaches flown for currency must also be flown to the appropriate minimums.


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Are there any aircraft that were grounded and later approved for flight?
Last year the Boeing 737 Max 8 was grounded after two fatal crashes.
Historically, are there any other commercial aircraft which were grounded (due to safety issues), and later “fixed” by manufacturers and approved by FAA and/or other authorities for flight?

I'm thinking about the Concorde which has had many changes after its crash (tanks, wheel,...) But it was not as used a the B737, and was not in production at that time, so I don't know if that counts.

Space Shuttle partially fits as Columbia crashed as an aircraft and then the long grounding followed. Just that it is not very "commercial".

The de Havilland Comet quickly comes to mind, with the airplane grounded after two catastrophic break ups in flight.  The Comet was returned to service once the problem had been identified and corrected in 1958.  Too late, however for the airplane to be a commercial success as the Boeing 707 had captured most of the commercial jet market in the intervening time.
So to was the McDonnell Douglas DC-10, which was grounded due to a faulty cargo door design, leading to two fatal accidents, but after operators implemented the required Airworthiness Directives from the FAA, the airplane was returned to service.
In fact many well known airframes have been temporarily grounded during their service lives then returned to service, including, but not limited to:

McDonnell Douglas DC-8
Aerospatsiale-British Aerospace Concorde
Boeing 767
Boeing 787
BAC One Eleven

Several aircraft were nearly grounded and faced public disfavor for a period of time thereafter.  The Boeing 727 was nearly grounded after 3 727-100s crashed in 1965, killing 131 people.  So, too, was the BAC 146 'WhisperJet', which was nearly grounded by the British government in 2000.
Military aircraft, too, have been temporarily grounded due to defects or service problems.  Lockheed's F-22 was grounded in 2011 after multiple pilots suffered hypoxic symptoms from the plane's malfunctioning OBOGS system.  The F-35 was temporarily grounded last November after a crash of an F-35B near Beaufort, SC.
Despite the best efforts of OEMs to conduct a rigorous and thorough development and flight test program to ensure a safe product, many potential problems simply can’t be identified until an incident or accident occurs in the fleet.  It’s virtually impossible to foresee every potential safety concern with a product that contains 4 million parts, 6 million lines of software code, terabytes of engineering data and tens of thousands of pages of operating protocols.  All of which must be able to function in perfect harmony and unison, without any conflicts.  Unfortunately much of what we know about aviation safety was paid for in the lives of the less fortunate.  Engineering OEMs strive to build better machines with each generation building upon the lessons learned from the past, but it’s not totally foolproof.

787 was not formally grounded, but a mandatory check and maintenance process was put in place which effectively grounded them for a short period until all aircraft could undergo those checks.

The Comet was the first thing that popped into my head.

The A380 following Qantas 32 also comes to mind. Qantas grounded their entire A380 fleet for a couple of weeks and didn't fully return them to service until a couple of months later (after 16 engines were repaired or replaced.) Singapore and Lufthansa also briefly grounded their fleets until they had inspected the engines and replaced the faulty ones. Those were the only 3 RR-powered A380 operators at that time, so it was effectively a worldwide grounding, at least briefly.

“All of which must be able to function in perfect harmony and unison, without any conflicts” Isn’t the whole point of redundant and compartmentalized components to solve this?

@Michael Not necessarily. The comment is meant to imply that many of the interactions between systems are simply unknown until a problem occurs. Think of all the times you’ve written a mess of code thinking it looked correct but doesn’t work when you run it and contains dozens of errors. Or was massively inefficient and caused conflicts with other sections of a program.  Now have that code driving a glorified aluminum can at 30,000 feet and just under the speed of sound with 200 people aboard

@jwenting, B787 was grounded for over two months. The EAD issued on 16th January 2013 required battery modification or other approved action before further flight, but no such action existed until AD 2013-08-12 issued on 26th April 2013. You may argue it wasn't formal as it doesn't use the word “grounded”, but it definitely meant just that.


text:
Is there a way to calculate the braking distance for a light aircraft?
PPL student, I train in a C152. Reviewing its POH I cannot find a method to estimate brake performance roll (as I would do with T/O roll).
Is there any method or rule to calculate brake roll in smaller aircraft, such as C152?
I believe this could be useful to calculate a NO-GO point in the RWY in case of not achieving the expected take-off performance.
*Side note: For the lack of a better method, I would use LDG performance rolls in the POH. But I consider that this is a rough estimation.

For the NO-GO point it's more useful to know what speed you should at some specific marker on the runway (like 500 ft or 1000 ft). Because on long runway if you take twice as much distance to get to rotation speed, you are not yet forced to abort to stop on the runway, but you already know your aircraft is underperforming and if you take off, the climb rate will probably be bad, so you should abort anyway. So for NO-GO point I suggest instead looking for way to derive it from the take-off distance required.

You're overengineering this problem (at least for the sort of flying you're doing as a student PPL)
Even if you could calculate the exact stopping distance required with full brakes application, lets say for argument sake that is 200m, do you know the exact point on the runway where you safely have 200m to stop? What about all the things that could affect that number

up/downslope
deterioration of brakes due to age
Tread thickness
surface water/oil/other contaminants

Can you make or assume some sensible factor(s) to add for these conditions, and if you can and you now calculate the braking distance is 300m do you know that exact spot on the runway where you should make your call whether to continue your  take off roll?

The way to do this without the overengineering is to follow the 70/50 rule. If you have not achieved 70% of your take off speed by half way down the runway then abort. Half way down your runway is easy enough to estimate.

Thanks! Sorry if you felt I was overkilling it. Not at all. In fact, you can see that I am asking for either a method (with all its complexity) or a rule (simple 70/50 rule as you are pointing).

@ppinto no need to appologise at all. It's very easy to get super enthusiastic about these sort of things but the best thing to do is listen to your instructor and concentrate on learning the skills theyre teaching you. there's plenty of time to learn everything else as you progress on. Good luck with your PPL

If the runway has markings, their spacing is typically known, so you can tell the 300 m left point (300 m ~ 1000 ft, at that is usually the aim point wide bars for the opposite runway).

@JanHudec the 300 figure was a purely fictional figure pulled from thin air. Also, I dont know where the OP trains but a lot of smaller airfields dont have anything like the kind of markings of a large airport. Mine for example has a centreline, and numbers either end and thats about it!

Of course, if you have a 1500 ft or 2000 ft runway, you can't land 1000 ft down, so the marking will be different, and much sparser. But is there nothing at all to go by? Some cones on the sides or something that you could find out position of in advance and then reference your NO-GO point (abnormal acceleration detection point) to?


text:
What is the best way for a VFR pilot to get a class B clearance when entering the DC SFRA?
When flying into BWI I need to enter class B airspace but also the Washington DC SFRA.
Assuming I have filed my flight plan to enter the SFRA correctly before my flight, how do I manage the radio calls in flight?
From my understanding:

I need to call the gate (e.g PALEO 132.775) to activate my flight plan and enter the SFRA, however they cannot clear me into the class B.
I need to speak to Potomac Approach (e.g. 119.0) to enter the class B.

Do I get clearance into the SFRA from PALEO first, telling them I'm going to BWI? Then, once I have clearance and a squawk code do I switch to BWI to get clearance into class B?

Any example radio calls would be greatly appreciated!

Is this not covered in the online SFRA training? (It may not be; genuine question.)

Nope. The example they give is flying to Manasses, which I think they use as they can fly under the class B shelf. They just say to tell ATC when you have the airport in sight

Just to cover all bases, if you have an instrument rating the simplest way is to file and fly an ordinary every day IFR flight. There will be no special clearances or requests.
For VFR folks. The rule is to be in contact with ATC while in the SFRA, but it does not need to be the VFR gate. The gate frequency is mainly to keep VFR chatter from cluttering IFR frequencies, the Gate and Potomac approach controllers are all in the same room and may even be the same person depending on how they divided sectors that day.
Class B is positively controlled airspace so there is no self navigation. You will not only get a clearance to enter, you will stay on their frequency (until they hand you off to tower or another sector) and follow navigation instructions the entire time you are in bravo.
Contact PALEO gate to activate the SFRA flight plan as normal, several miles from either SFRA or class Bravo. If it isn't clear from their communications make sure PALEO knows you are landing BWI and need to enter class bravo.
PALEO should then just hand you off to the approach frequency. Switch to that frequency, "Potomac approach, N1234 with you", wait for response and answer questions[eg state request, aircraft type, ident, etc.], request to enter bravo for landing at BWI visual approach, (If they didn't beat you to it), follow vectors and altitudes reading them back.
But make sure you hear an explicit "cleared into class bravo" before entering bravo. Ask if you are not sure that you heard it even if they gave you vectors.


text:
How do the contrarotating turbines work in the F-119-PW-100?
I was reading about the F22 Raptor and found out that its powerplants use  contrarotating turbines. How does this work
Also, if the spools and their connected compressors are rotating in opposite directions, won't the stators and their angles and such be different?
And, if it reduces a row of stators then the compressor which acts as a stator in the last stage, how does it change the AOA according to the flow rate, if it works like a stator?
Also, the F119-PW-100 has 3 low pressure compression stages and 6 high pressure ones. Which means it should have 10 stator stages. So, if a row of stators goes away, how many stator stages remain.
I'm sorry if I'm wrong somewhere or I reached conclusions which aren't right. I'm a 16 year old enthusiast, and I'm just curious.


text:
Why were the F-35B lift fan doors changed after flight testing?
Why were the F-35's lift fan doors redesigned from those used during flight tests? The original design had two main doors which opened to each side, rather than the “car hood” style door used in production F-35B aircraft.

I don't suppose you could edit your question and add pictures to it?

It was due to flow issues. Here's an excerpt form Air & Space Magazine

We discovered a few things that would need to change before the
  aircraft entered production. On the X-35B’s STOVL variant, the doors
  above the lift fan had a bi-fold arrangement: They folded and slid
  outward, creating an opening for air to enter the fan. However, when
  the airplane was slowed to a hover, the air flowing across the top of
  the aircraft would not on its own make the turn into the fan
  efficiently; it needed to be guided. On the production F-35B there is
  a different arrangement: Instead of two doors sliding open, a single
  door, hinged aft, lifts up and acts like an air scoop, helping to
  funnel the air into the fan. But the new design of the lift fan cover
  created additional challenges for the two auxiliary air inlet doors
  that sit right behind it. Not all the air is channeled into the fan,
  and at higher speeds, the air that flows around its raised cover is
  turbulent, causing the open doors on the auxiliary air inlets to
  vibrate. The hinges on those doors, therefore, had to be strengthened.

You'll also note that the Auxiliary Lift Fan doors changed (bigger, hinged on outboard edges) as a result of the main door change.


text:
Is a foreign flight review sufficient to keep FAA currency for an FAA foreign-based PPL?
I have a foreign-based PPL issued by the FAA. According to the regulation of my original (non-FAA) PPL, I am required to accomplish a biennial flight review with an authorized instructor in my country. I had a flight review less than a month ago to meet this requirement.
During a checkout flight in the US, the local CFI stated that the flight review must be conducted by an FAA-authorized CFI - therefore the flight review I had in my home country (less than a month ago) is not sufficient. He stated that FAR §61.56 requires I have "Accomplished a flight review given in an aircraft for which that pilot is rated by an authorized instructor", while FAR §61.1 defines an "authorized instructor" as "(ii) A person who holds a flight instructor certificate issued under part 61 of this chapter and is in compliance with §61.197"
The CFI that approved my last flight review is authorized by the local authorities in my country, but not by the FAA under part 61.
On the other hand, as far as I know, a foreign-based FAA PPL should be valid as long as the original PPL (it is based on) is valid, without any special additional requirements from the FAA.
In my case, my original PPL meets all the requirements by the local authorities in my country.
Am I still required to have another flight review, in the US, approved by an FAA-authorized CFI?

Welcome to aviation.SE! Does this question help? It seems to be very similar. Note the legal interpretation mentioned in this answer.

When getting the FAA license based on a foreign license there is no test at all, as it is totally dependent on the foreign license stays current. It is a bi-lateral agreements that allow you you fly in a country with a U.S. license and the foreign equally get same right here. Have not seen a specific ruling on the BFR but it does not make much sense to require a U.S. BFR in a certificate that is totally dependent on a foreign certificate staying current.
For my situation, living in the US permanently the situation became problematic the other way, to get a foreign medical and a foreign BFR while doing all my flying in the US, so I took the written and the practical test here after a few hours of instruction and got my PPL issued from FAA with no dependent foreign license.


text:
How does one determine the elevation on a sectional?
(Refer to figure 21) How does one determine the elevation variation of the light tan area between Minot (area 1) and Audubon Lake (area 2)?

A. 2,000 ft to 2,500 ft MSL.
B. 2,000 ft to 2,700 ft MSL.
C. sea level to 2,000 ft MSL.

I want to thank everyone for the help.  I made an 88 on my Drone certification that I took today (10/11/2018)

You seem to be asking two different questions: a) how to determine terrain elevation on a sectional, and b) what is the correct answer to this FAA test question?
First, there are multiple ways to determine terrain elevation on a sectional, as the FAA's Chart User's Guide says:

Our Aeronautical Information Specialists are devoted to showing the
  contour of the earth and any obstructions clearly and accurately on
  our charts. We use five different techniques: contour lines, shaded
  relief, color tints, obstruction symbols, and Maximum Elevation
  Figures (MEF).

In addition to those five things, sectionals also show airport elevations, perennial lake elevations and spot elevations (and maybe others). You can find details of all those things in the Guide.
Second, what's the correct answer to that specific test question? Others have already answered that, but I suspect that the FAA is expecting you to use multiple methods, e.g. use the logic from ymb1's very neat answer, confirmed by looking at obstacle elevations and MEFs. But that's my own speculation, I don't know for sure how they think you should determine the elevation. The main point is just that there are multiple ways to do it, depending on what features and information are on the specific sectional area that you're looking at.

As you thanked us in advance, I apologize in advance for this answer as I don't really know but this is my hunch.
Since it is tan, the key says it is between 2000' and 3000'. Then, from what I can tell there are peaks every now and then. If you look at the peak west of Minot it reads 2526' while the one next to Audubon Lake reads 2267'. Just to make it more accurate, I would also take into account the peak in the middle that is 2511' . I would then average these and see where it fits. This averages out to ~2434.66'. Thus my answer would be A.

seems like a good hunch. Hopefully someone will verify. thanks again.

Ya no problem. Tbh I'm in highschool and I'm taking an aeronautics class, but we haven't don't stuff like that yet. Soooo.... :P Well Good luck on your test.

But I notice something now, the area around Audubon lake is green, meaning that its elevation is lower. Between 1000 and 2000. So I am probably wrong.

Unless the question, is only referring to the tan area, in which my answer might still be correct.

Oh, the answer was A. 2000 to 2500, but I still need verification if it's done the way you thought or if there is another way to determine it.

Those aren’t peaks. They are buildings or clusters of buildings and a radio tower. The radio tower is listed as 3149 MSL and 1031 AGL. Subtract the two and you get ~2100. If I recall correctly manmade obstacles are rounded and 100' added, so the terrain is about 2,000' MSL there. You can do the same for the buildings. Also, Poleschook airport is listed as being at 2245 MSL and Semchenko is 2065. So everything is around 2000-2500'. There are no contour lines that I can see so the answer is 2,000-2,500.


text:
What was the last rocket-plane?
Starting with the legendary Heinkel He 176, these unorthodox planes broke the sound barrier and other records. My question is: What was the last rocket plane to be produced?

Yeah, or the Opel glider, launched by firework-type rocket motors.

Google for Oper-Sander or Julius Hatry RAK.1 and you will be able to shift the birth of rocket planes quite a bit forward from the He-176.

It would depend on just where you draw the line between "plane" and "spaceship". Answers could be the Rocket Racing LEague's "Rocket Racer", or Virgin Galactic's "SpaceShipTwo" or even if you want to push it SPaceX's StarShip, if you accept a definition of plane that fits "flies and lands using active aerodynamic support"

Spaceship Two https://en.wikipedia.org/wiki/SpaceShipTwo currently flying (at least as of July 2021: https://www.theverge.com/2021/9/29/22701195/faa-virgin-galactic-spaceshiptwo-cleared-investigation )

D'oh!  I forgot about Virgin Galactic!  Didn't they fly paying passengers (or at least non-employees) just days before New Shepard's first human-carrying flight?

@ZeissIkon they did. Not sure I'd call it an rocket aircraft rather than a winged rocket but that's semantics.

It glides when the rocket is shut down, and briefly before ignition, just like the X-15 did -- but it's more advanced in many ways (though designed mainly for altitude rather than speed).  To my eye, it's an airplane with a big rocket engine.

@Zeiss Ikon: Though wasn't the X-15 primarily designed for altitude?  At least that's what I remember: several military X-15 pilots getting "astronaut wings" because of the altitude they reached: https://www.spaceline.org/united-states-manned-space-flight/us-astronaut-selection-drafts-and-qualifications/x-15-astronauts/

X-15 was designed both for altitude and speed -- and there's no way Spaceship Two would hold up to the Mach 6 the X-15's record flight obtained (melted some stainless steel parts of the airplane).  Spaceship Two is only made to go high and let passengers have maximum microgravity time.

As much of a space nerd as I am, I can't believe I forgot about spaceplanes!

Rocket Racer was a one-design air racing class founded in 2005, to be powered by a small ethylox rocket engine.  The airframe was a Velocity (kit plane) with some modifications (Rocket Racing League bought the manufacturer, which has since spun off and is back to producing kits) -- and while it's not a commercial production aircraft, three were built between 2006 and 2008.  At least one demonstration aircraft flew several times, demonstrating (among other things) rapid turn around (a big deal in rocket circles), ground takeoff and sufficient endurance to race, and safe operation.
The racing league that was to have featured these airplanes failed on financial grounds, and production was halted by the other teams that were originally to have founded the league, but these were solely rocket-powered racing aircraft built in the 21st century!


text:
Could a paramotor pilot sign a legal waiver saying that he is responsible for anyone's injuries if he crashed?
Per FAR part 103.15

No person may operate an ultralight vehicle over any congested area of a city, town, or settlement, or over any open air assembly of persons.

However something got me thinking about this. If the paramotor pilot(s) were to legally enter an airshow, if they signed a waiver stating that they are responsible for any injury caused by them, or if the occupants signed a waiver saying that they are risking their life being at the airshow, could the paramotor pilots use that a "reason" to bypass FAR part 103.15?

Welcome to aviation.SE! If you don't get a good answer here, you might try asking on law.SE instead. The FAA can waive some of their own regulations, but you seem to be asking if an individual can waive them personally, and that seems more like a legal question than an aviation one to me.

The only ways around a FAR are:

Exceptions explicitly written into that FAR,
General exceptions like emergencies, or
A specific waiver from the FAA itself.

The former two do not apply here.
The latter may or may not be difficult to get, depending on which rule, why you want to break it, and what alternate measures you propose taking that would mitigate the risk that the rule was intended to protect against.
Airshows by their nature get lots of waivers, and you’ll need to work with the organizer to get your specific waiver request included in the giant pile they’ll be submitting. Assuming they are interested in what you propose to do at their show, of course.

My experience is limited, but typically the airshow organizer obtains a blanket waiver for all participants.  It is specific in what you can and cannot do.  I don't remember signing anything as an individual.

There is no need to sign a document that  states one accepts responsibility for any injuries caused by them: the pilot in command is, by default, responsible for any damages he/she causes by operating the aircraft.
As for the second part, the visitors/occupants at the airshow signing a waiver, I'm sceptical as to how binding this would be. The signee might not be able to sue the organizers or the pilot for any damages, but whatever the contract might hold, the pilot would still have been in violation of FAR 103.15, and the organizers would definitely be under criminal investigation for knowingly organizing an event that (partially) consisted of actions that were prohibited by FAR 103.15
Now: one might ask how the heck can these events be organized? Well, as Pondlife pointed out, there is a possibility of acquiring a permit, but why not simply arrange flightpaths such that the pilots need not fly over "any open air assembly of persons". It's really not that hard.
I must admit I'm not a FAR specialist, and to really give a correct, complete and concise answer would require knowing a whole lot more that just two paragraphs of the regulations. There may be exceptions when dug deeper.

14 CFR 103.5:

No person may conduct operations that require a deviation from this
part except under a written waiver issued by the Administrator.

The pilot can sign anything they want - and the airshow organizers might indeed ask them to sign other waivers - but they would still need the FAA to give them a written exception to 103.15. (See this related question about part 91.)
If you're asking a 'meta question' about whether an individual can opt out of a government regulation by explicitly accepting the consequences, law.SE would be a better place to ask. Although I think it's fairly obvious that the answer is "no", otherwise regulations would be completely meaningless.

Do you know of any federal rule you can "bypass" by saying you agree to accept the consequences?
If you want to go speeding in your Ferrari, can you sign a paper that says you'll pay for any injuries and property damage?  Do you think the police will then say, "Oh, look! He signed a piece of paper.  We cannot issue a speeding ticket or arrest him now, because his signature is on a form!"
Can you "bypass" drunk driving rules if you're rich enough to pay for damage you cause?  OF COURSE NOT.
The "ultra-lights over congested areas" rules are about safety, not "financial cost" or "legal liability".   Neither a pilot, nor someone on the ground can agree to bypass a safety rule.
NO, just plain "no".
You cannot "opt-out" of Laws and Regulations.

That’s a little vague from a legal perspective.
For this scenario, the ‘waiver’ you suggest carries no legal weight as most local, county, and state jurisdictions defer air law over to the FAA and federal regulations under Title 14 of the CFR.
To begin with, an ultralight pilot acting as PIC of said aircraft is, by definition, directly responsible for, and the final authority on, the operation of that aircraft.
In order to fly said aircraft over an open venue of persons, you would need an FAA issued waiver of §103.15 plus additional waivers for other regulations, depending on the kinds of display in question eg aerobatics, etc.
Now you may still be held liable for property damage, injury or death with an accident if the root cause is determined to be pilot recklessness, incapacity or neglect in violation of §103.9.  Circumstances also would dictate weather a local or federal prosecutor would seek to pursue criminal charges against you. A determined §103.9 or §91.13 violation would make you vulnerable to a civil tort, particularly wrongful death if your actions resulted in loss of life.
Companies promoting airshows may require performers to sign legal documents associated with her performances where the performer agrees that the promoter assumes no liability by the performer should an accident occur.  I’m not totally sure on the details of that, but that’s not uncommon.


text:
How did the waypoint ULURU get its name?
Can anyone explain how the waypoint ULURU near Sandspit, BC Latitude    53° 6' 1.00" N Longitude 131° 38' 13.00" W was named, when Uluru is a very large monolith in Australia also known as Ayers Rock?

Related, possible dupe: https://aviation.stackexchange.com/questions/12791/how-unique-are-waypoint-names-supposed-to-be

Related about naming but not duplicate for sure.

The ICAO rules for waypoint names are very loose. They have to be five characters long, they can't be close to another waypoint with the same name (where the definition of "close" can vary from jurisdiction to jurisdiction; in most cases, they must be unique within a country), and (in some jurisdictions) they have to be pronounceable. Beyond that, it's up to whatever body was in charge of planning the airspace to pick a name.
So, the answer to your question is "because somebody in the TCCA liked the name".

Sometimes, fix names are just made up out of whole cloth, having no connection to anyone, anything, or any place.  In the USA, fix name reservations are maintained by each ARTCC for use within that ARTCC's Flight Information Region.


text:
Is this description of lift and drag coefficients correct?
In my course (Principles of Flight) written:

The effect of CLift is not linear. This means that Lift doubles for
double the lift coefficient.

And

The effect of CDrag is linear. This means that for double the drag
coefficient the drag force doubles.

If it's correct? And if yes, why effect of CL is not linear? Seems the same for me: coefficient doubles - force doubles.

The quoted text is in error. Lift (for a given airspeed) is directly (linearly) proportional to the lift coefficient.  Lift (for a given lift coefficient) is proportional to airspeed squared.  Likewise, Drag (for a given airspeed) is directly (linearly) proportional to the drag coefficient.  Drag (for a given drag coefficient) is proportional to airspeed squared.

Thank you for explaining